Photonics Dictionary

With respect to pictorial displays, the ratio of the width to the height. The television standard in the US is 4:3. High-definition or wide-screen television will have a ratio of 16:9.

An atomic absorption spectrometer (AAS) is an analytical instrument used to determine the concentration of specific chemical elements in a sample by measuring the absorption of light at...

The efficiency of scattering by an atom in a particular direction, expressed as: where AA is the amplitude of the wave from the atom and AE is the amplitude of the wave from a free electron.

Attenuation refers to the gradual loss or reduction of intensity, force, or magnitude of a particular property as it propagates through a medium or travels over a distance. This concept is prevalent...

The radiation-free transition that takes place within an ion, in which inner-shell vacancies in neutral atoms are filled by outer-shell electrons, thereby transferring energy to other electrons,...

The green line, in the spectrum of the aurora borealis, that has a wavelength of 5577 Å; it is caused by a forbidden transition in oxygen.

Autofluorescence refers to the natural emission of fluorescence exhibited by certain biological structures or molecules when exposed to light. Unlike fluorescence that results from the application of...

In astronomy, the method of deliberately viewing objects with peripheral vision to take advantage of the eye's greater sensitivity to faint light a few degrees from the optical center.

An axicon is a type of optical component characterized by its conical shape and its ability to transform a collimated Gaussian beam of light into a ring-shaped beam with a gradually increasing...

A device containing two opposed quartz wedges of equal angle, one wedge being movable along its length by a micrometer screw. The wedges are cut so that their fast directions are along, and...

The principle stating that two diffraction screens, one being exactly the negative of the other, will form the same diffraction patterns.

Refers to a display or screen that is illuminated from behind; the light is transmitted as opposed to reflected.

In semiconductor physics, the term bandgap refers to the energy range in a material where no electronic states are allowed. It represents the energy difference between the valence band, which is the...

Bathymetric lidar is a remote sensing technique used to measure the depth of water bodies and map underwater terrain features. It employs lidar (Light Detection and Ranging) technology, which uses...

In computer graphics, the point on the display screen where the electron beam is located before the display instruction is executed. On directed beam display points, vectors and other graphic...

A characteristic of optical fiber used to calculate the fiber's ability to maintain polarization. The beat length describes the length required for the polarization to rotate 360 degrees. For a given...

Two formulas used in diffractometer analysis, the first giving the individual diffraction patterns of each aperture, the second representing the constant of the degree of an incoherent circular...

A facility selected by mutual agreement of the user and the prospective vendor to test a prototype before it is offered for sale.

A device having a pair of decentered lenses, one for each eye, that focuses on a single object as a magnifier. It is often supplied with a forehead fixture or an elastic headband to leave the hands...

Light interference fringes that can be viewed on a screen near a biprism.

In computer graphics, the assignment of each pixel on a display screen to its own switch in the computer memory.

A blackbody source, often simply referred to as a blackbody, is a theoretical or practical physical object that absorbs all electromagnetic radiation incident upon it and emits radiation in a...

A Bose-Einstein condensate (BEC) is a state of matter that forms at temperatures close to absolute zero. It is named after Satyendra Nath Bose and Albert Einstein, who independently predicted the...

Crystal growth method that resembles static freeze, but that induces growth by removing the ampoule from the furnace so that the freezing-point temperature gradient is unchanged during the growth...

An instrument for measuring the brightness (luminance) of a scene. It may be a spot meter, covering an area of a degree or less, or an averaging meter, covering a broad area of the scene. Brightness...

The degree to which a pixel in a digital image represents the analog brightness of the corresponding point in the original image. It is dependent largely on the number of bits devoted to representing...

Brillouin microscopy is a non-invasive imaging technique that utilizes Brillouin scattering to measure the mechanical properties of materials at the microscale. This advanced optical technique...

A mercury vapor discharge lamp that has cadmium added to emit radiation in the red region as a complement to the mercury vapor's blue and green radiation.

The three lines in the spectrum of cadmium that have the purest radiations and that were first used by Michelson to calculate the standard meter.

A calcium indicator is a molecule that is sensitive to changes in calcium ion (Ca2+) concentrations in biological systems. These indicators are commonly used in various fields, including cell...

Calorimetry is a branch of science that involves the measurement of heat flow in physical or chemical processes. It encompasses various techniques and instruments used to quantify heat transfer,...

Carbonization is a process in which organic materials are heated in the absence of air, leading to the decomposition of the material and the production of carbon-rich residue. During carbonization,...

Carrier injection refers to the process of introducing charge carriers (either electrons or holes) into a semiconductor material. Semiconductors are materials with electrical conductivity between...

A two-mirror lens design used in astronomical telescopes, the primary being a parabola, the secondary a smaller hyperbola. The image formed is free of spherical aberration and color and is located...

A cathode is an electrode through which electric current flows out of a polarized electrical device. In different contexts, the specific role and behavior of the cathode can vary, but it generally...

The luminous trace formed on the cathode-ray tube screen by the motion of the electron beam.

A vacuum tube with an electron gun at one end and a fluorescent screen at the other. Electrons emitted from a heated filament are accelerated by a series of annular anodes at progressively higher...

Computer hardware or firmware that accesses character patterns stored in read-only memory and displays them at specific coordinates on a screen.

Chirality is a property of certain molecules and objects in which they are non-superimposable on their mirror images. In other words, a chiral object or molecule cannot be exactly superimposed onto...

The plane diagram produced by plotting one of the three chromaticity coordinates (X,Y,Z) against another. The most common diagram is the CIE (X,Y) diagram, which is plotted in rectangular coordinates.

The application of a cine camera in recording the images on a fluorescent screen. When x-rays are used to produce the screen images, this process is referred to as cine-radiography.

The photographic filming of the action of x-ray images recorded on a fluorescent screen by means of large lens apertures and highly sensitive filters.

Circular dichroism (CD) is a spectroscopic technique used to study the structural characteristics of chiral (asymmetric) molecules, particularly biomolecules like proteins, nucleic acids, and certain...